Molecular Basis of Postischemic Maladaptation in the Insulin Resistant Heart

摘要 2型糖尿病已经达到流行的程度，是中国冠心病的主要原因。 美国。胰岛素抵抗是2型糖尿病的一个标志，与高出2到4倍的风险有关。 急性心肌梗死(MI)后的心脏发病率和死亡率。该项目的目标是 胰岛素抵抗与心肌梗死后心脏恢复不良的分子机制及其应用 这一知识有助于制定促进糖尿病患者心功能恢复的治疗策略 在再灌流时。解偶联蛋白3(UCP3)是一种具有抗氧化功能的线粒体阴离子载体蛋白 参与长链脂肪酸(LCFA)的代谢。2型患者肌肉中UCP3含量低50% 糖尿病患者与健康对照组比较。在小鼠的心脏中也观察到类似的下降 以及患有胰岛素抵抗和2型糖尿病的大鼠。在老鼠身上使用CRISPR/Cas9靶向突变，我们已经 收集的初步数据显示，心脏UCP3水平下降50%足以显著 有损于缺血后的收缩恢复。我们的结果进一步表明，功能恢复下降 缺血后胰岛素抵抗和UCP3缺陷心脏的发生是由于其氧化LCFA的能力有限所致 再灌注是一种缺陷，可以通过供应中链脂肪酸(MCFA)作为替代燃料来修复。 除了生物能量缺乏外，已知LCFA氧化受损还会导致长链的有毒积累。 神经酰胺和增加氧化应激。因此，我们假设UCP3的减少会损害 限制心肌LCFA对胰岛素抵抗心肌梗死后心脏收缩功能的恢复 氧化，增加线粒体功能障碍，增加心肌细胞在再灌注时的死亡。 三个目标将在饮食、药物或遗传的小鼠和大鼠模型中解决这一假说。 多系统方法中诱导的心肌胰岛素抵抗或UCP3缺乏症(减少40-50%) 结合在体心肌梗死/再灌流模型，从心脏跳动到线粒体分离。目标1将 检测UCP3缺乏及其逆转对心脏结构和功能恢复后的影响 心肌梗死/再灌注。目的2将研究UCP3缺乏对线粒体的分子后果 缺血/再灌注时心脏功能与氧化代谢的关系。目标3将测试一种新陈代谢 基于增加心脏MCFA供应的干预可以逆转这些异常。我们预料到了这一点 揭示导致2型糖尿病患者预后不良的新分子机制的项目 在心肌梗死/再灌注后，这将为进一步研究以MCFA为基础的治疗提供基础 作为一种代谢策略来改善接受心肌梗死后再灌注的T2 DM患者的心脏结局。

ABSTRACT Type 2 diabetes has reached epidemic proportions and is a leading cause of coronary heart disease in the United States. Insulin resistance, a hallmark of type 2 diabetes, is associated with a 2 to 4 times higher risk of cardiac morbidity and mortality following acute myocardial infarction (MI). The goals of this project are to elucidate the molecular mechanisms linking insulin resistance to poor cardiac recovery after MI and to apply this knowledge to develop therapeutic strategies for improving recovery of cardiac function in diabetic patients at reperfusion. Uncoupling protein 3 (UCP3) is a mitochondrial anion carrier protein with antioxidant properties involved in the metabolism of long-chain fatty acids (LCFA). Muscle UCP3 content is 50% lower in type 2 diabetic patients compared with healthy control subjects. A similar decrease is observed in the heart of mice and rats with insulin resistance and type 2 diabetes. Using CRISPR/Cas9-targeted mutation in rats, we have gathered preliminary data showing that a 50% decrease in cardiac UCP3 levels is sufficient to significantly impair contractile recovery following ischemia. Our results further suggest that decreased functional recovery of insulin resistant and UCP3 deficient hearts after ischemia is caused by a limited capacity to oxidize LCFA at reperfusion, a defect that can be rescued by supplying medium-chain fatty acids (MCFA) as an alternative fuel. Besides the bioenergetic deficit, impaired LCFA oxidation is known to cause a toxic accumulation of long-chain ceramides and to increase oxidative stress. Therefore, we hypothesize that decreased UCP3 impairs the recovery of systolic function in insulin resistant hearts following MI by limiting myocardial LCFA oxidation, increasing mitochondrial dysfunction, and increasing cardiac myocyte death at reperfusion. Three aims will address this hypothesis in mouse and rat models of dietary, pharmacologically, or genetically induced myocardial insulin resistance or UCP3 deficiency (40-50% decrease) in a multisystem approach combining in vivo models of MI/reperfusion to isolated beating hearts to isolated mitochondria. Aim 1 will examine the effect of UCP3 deficiency and of its reversal on cardiac structural and functional recovery post MI/reperfusion. Aim 2 will investigate the molecular consequences of UCP3 deficiency for mitochondrial function and cardiac oxidative metabolism during ischemia/reperfusion. Aim 3 will test whether a metabolic intervention based on increasing supply of MCFA to the heart can reverse these abnormalities. We expect this project to reveal a novel molecular mechanism responsible for the poor prognosis of type 2 diabetic patients following MI/reperfusion, and that it will provide the basis for additional studies to test MCFA-based treatments as a metabolic strategy to improve cardiac outcomes in T2DM patients undergoing reperfusion after MI.